There are conventionally known services for selling digital contents such as music data wherein users can tentatively enjoy part of the contents before the users purchase the contents. In such services, users purchasing music data for example can preview a particular part such as a melodious part of an entire stretch of a musical piece before the purchase. There have been proposed such preview services of music wherein contents are provided in accordance with users' preferences estimated based on use history of the users (see, e.g., Japanese Patent Application Publication No. 2009-266083).